Liquid pump

ABSTRACT

A liquid pump having a piston head carried by a piston rod and located in a cylinder between an inlet and outlet, the head being of a type that enables passage of fluid in the cylinder from the inlet side of the head to the outlet side upon head movement in a first direction, and delivering fluid on the outlet side of the head to the outlet and drawing fluid from the inlet into the inlet side upon head movement in the opposite second direction. A motor means includes a rotatable eccentric engageable with a follower carried by the piston rod to urge the piston means away from one limit of its movement and in the first direction, while a spring tends to return the piston means to said one limit of its movement in the second direction. A check valve communicates with the outlet and enables fluid flow only in the direction from the cylinder through the outlet, and a metering valve means communicates with the outlet and regulates liquid flow delivered by the piston means through the outlet at a predetermined rate.

United States Patent McDougall [451 Apr. 11, 1972 [54] LIQUID PUMP Primary ExaminerWilliam L. F reeh [72] Inventor. Franklin M. McDougall, St. Louis, Mo. Atmmey Cohn and Powell [73] Assignee: Dema Engineering Co., St. Louis, Mo. 22 Filed: July 18,1969 [57] ABSTRACT A liquid pump having a piston head carried by a piston rod [21] Appl' 842310 and located in a cylinder between an inlet and outlet, the head being of a type that enables passage of fluid in the cylinder l7/471, 417/441 from the inlet side of the head to the outlet side upon head [51] Int. Cl ..F04b 49/00 ov ment in a first direction, and delivering fluid on the out- Field of Search --l03/20; 417/4 5 let side of the head to the outlet and drawing fluid from the 417/214, 212 inlet into the inlet side upon head movement in the opposite second direction. A motor means includes a rotatable eccen- References cued tric engageable with a follower carried by the piston rod to urge the piston means away from one limit of its movement UNITED STATES PATENTS and in the first direction, while a spring tends to return the 2,064,750 12/1936 Hurst ..4l7/2l4 piston means to said one limit of its movement in the second 2,553,321 5/1951 Ratcherw 7/ direction. A check valve communicates with the outlet and 2,133,510 12/1939 Thomas.- ...-l03/203 enables fluid flow only in the direction from the cylinder 2,753,304 1956 9 103/44 through the outlet, and a metering valve means communicates 2,759,665 8/1956 Wllbuf 230/235 with the outlet and regulates liquid flow delivered by the 5 10 4/1957 y g 103/50 piston means through the outlet at a predetermined rate. 3,143,969 8/1964 Eames et al... ..l03/42 3,223,045 12/1965 Shoppe 103/150 2 Claims, 4 Drawing Figures \firimim PATENTEDAPR 11 I972 SHEET 1 [IF 2 INVENTOR FRANKLIN M. McDOUGALL BY wmmw ATTORNEYS SHEET 2 OF 2 nm, mm R mm PATENTEDAPR 1 1 1912 mm mm INVENTOR FRANKLIN M. McDOUGALL ATTORNEYS BACKGROUND OF THE INVENTION The typical motor-driven injector employs a small reciprocating pump of constant displacement. The displacement is changed by mechanical adjustment which usually requires the stopping of the pump while the change is being made. Setting such a unit to an extremely small delivery rate requires a high grade of precision in the manufacture of the parts and in making the adjustment.

The two principal objections to such heretofore conventional mechanical injectors are the length of time required to prime the unit and the uncertain repriming when set for a small displacement.

SUMMARY OF THE INVENTION This invention relates generally to a liquid pump that discharges at adjustable flow rates, and more particularly relates to an improved mechanism for injecting a liquid wetting agent or other chemical into water flowing through a closed conduit.

Although suitable for many other uses, this liquid pump is adapted for the injection of a small quantity of liquid rinse additive into the rinse water of a mechanical dishwasher.

The liquid pump will operate efficiently at low flow rates and requires no mechanical adjustment of the piston stroke, the delivery rate being adjusted hydraulically rather than mechanically. The piston stroke is not limited by mechanical adjustment for a particular low flow rate, but rather stroke is whatever is needed to deliver the flow rate as determined by an adjustment needle valve. The pump will stop pumping without stalling under adverse conditions such as exist when the delivery line is blocked. It will automatically shift to maximum displacement during priming and then revert to the partial displacement to which it has been set for delivery of flow at a predetermined rate. Change in viscosity of the liquid has no detrimental effects. The pump will handle elastic fluids such as a liquid with entrained air or a volatile solvent.

The piston head is located in a cylinder between an inlet and an outlet, the head being of a type that enables passage of fluid in the cylinder from the inlet side of the head to the outlet side upon head movement in a first direction, and which delivers fluid on the outlet side of the head to the outlet and draws fluid from the inlet into the inlet side upon head movement in the opposite second direction. A resilient means tends to urge the piston means to one limit of its movement in the second direction, while a motor means engages the piston means and intermittently urges the piston means away from the said limit and in the first direction. The liquid flow delivered by the piston means through the outlet is regulated by a metering means that communicates with the outlet. The fluid flow from the cylinder through the outlet is restricted to one direction by a check valve means.

The motor means includes a rotatable eccentric, and the piston rod includes a follower that is urged against the eccentric by the resilient means.

An inlet line interconnects the inlet with a reservoir containing the liquid additive, the inlet line introducing the liquid additive into the cylinder through the inlet. An outlet line interconnects the outlet with a flow passage, which can be the rinse line of a dishwasher, and delivers the liquid additive from the cylinder to the passage.

Either one or both of the metering valve means and the check valve means can be incorporated as a part of the pump body or can be located at the rinse line while the piston can be located at a remote location.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing the liquid pump in use on a dishwasher;

FIG. 2 is a cross-sectional view showing the liquid pump, in simplified structure, connected to a flow passage;

FIG. 3 is a top plan view of the liquid pump shown in detailed structure, and

FIG. 4 is an enlarged, cross-sectional view of the pump assembly as taken on line 4-4 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now by characters of reference to the drawings, and first to FIG. 1 in which the liquid pump is shown associated with a dishwasher, it will be understood that the dishwasher referred to by 10 includes a wash compartment 11 in which the spray lines and nonles 12 are located. It will be understood that this liquid pump can be utilized in many fields and that a dishwasher is illustrated merely to show one environment. A rinse line 13 is connected to spray lines and nozzles 12, as is conventional. The water flow through the rinse line 13 is controlled by a solenoid valve 14.

The liquid pump generally indicated by 15 is carried by the dishwasher 10 and is operatively connected to the rinse line 13, the rinse line 13 constituting a flow passage. As will appear upon later detailed description of parts, solenoid valve 14 and the liquid pump 15 are operatively connected by an electric circuit 16.

A simplified structure of the liquid pump 15 is illustrated in FIG. 2. The pump includes a body 17 provided with a cylinder 20, the cylinder 20 having an inlet 21 and an outlet 22.

A piston means generally indicated at 23 includes an elongate piston rod 24 reciprocatively mounted in the body 17. A seal between the piston rod 24 and the body 17 is provided by an O-ring 26 carried by the rod 24.

Carried by the rod 24 and located in the cylinder 20 between the inlet 21 and outlet 22, is a piston head 27. In the embodiment of FIG. 2, the piston head 27 consists of a flexible, cup-shaped washer that engages the peripheral wall of cylinder 20, and is of a type that enables passage of fluid in the cylinder 20 from the inlet side of the head 27 to the outlet side upon head movement in a first direction (toward the right in FIG. 2), and which delivers fluid on the outlet side of the head 27 to the outlet 22 and simultaneously draws fluid from the inlet 21 into the inlet side upon head movement in the opposite second direction (toward the left in FIG. 2).

The external end of piston rod 24 is provided with a follower 30. Located about the piston rod 24 is an external spring 31, constituting a resilient means, one end of spring 31 engaging the body 17 and the other end engaging the follower 30. The spring 31 tends to urge the piston means 23 to one limit of its movement in the second direction.

A reservoir 32 of liquid additive 33 such as a rinse additive to be added into the rinse water of a mechanical dishwasher, is operatively connected to the inlet 21 by an inlet line 34. The liquid additive 33 is fed from the reservoir 32 into cylinder 20 through inlet 21.

The body 17 is provided with a chamber 35 in communication with the cylinder 20 through the outlet 22. A check valve means is located in the chamber 35, the check valve means including a ball 36 adapted to close the cylinder outlet 22, and a spring 37 engaging the ball and tending to urge the ball 36 toward the closed position. A tube 40 communicates and cooperates with the chamber 35 to provide an outlet line that interconnects the cylinder outlet 22 with the rinse line 13, constituting the flow passage, the outlet line delivering the liquid additive from the cylinder 20 to the rinse line 13.

A metering valve means 41 communicates with the outlet 22 and regulates the rate of liquid flow delivered by the piston means 23 through the outlet 22. The metering valve means 41 includes a body 42 connected to the outlet line and mounted to the rinse line 13. Threadedly mounted in the valve body 42 is a needle valve 43. The needle valve 43 is selectively adjustable to regulate flow rate precisely through the outlet line.

In FIG. 2, the metering valve means 41 is shown attached to the rinse line 13 remote from the pump body 17. It will be understood that either or both of the check valve means and metering valve means 41 can be incorporated as a part of body 17 or located remotely from body 17 for mounting at the rinse line 13. It is preferred that the metering valve means 41 be located downstream of the check means.

Mounted on and rotatable with a driven shaft 44, constituting a part of a motor means which will later be described in detail, is an eccentric 45 engageable with the follower 30, the eccentric 45 urging the piston means 23 away from its said outermost limit and in the first direction. When the pump is operating, the eccentric 45 is intermittently urging the piston means 23 in a direction away from the axis of shaft 44 and inwardly of body 17 in the first direction.

The detailed construction of the pump is best shown in FIGS. 4 and 5. The simplified structure of FIG. 2 is provided for easier understanding of the principle involved and the operation which will later be discussed.

In FIG. 4, the body 17 is mounted to a bracket plate 46 that can be a part of the dishwasher 10. Provided in body 17 is the pump cylinder 20. The cylinder inlet 21 is provided by an inlet fitting 47 adapted to be attached to the inlet line 34. The cylinder outlet 22 places the cylinder in communication with the chamber 35. The outlet line includes the chamber 35 and an interconnecting passage 50 that is placed in communication with the rinse line 13 through a tube 40, such tube 40 being connected to body 17 by fitting 51.

The piston means 23 includes an elongate piston rod 24 slidably mounted in a plug 52 fitted into the body 17 and closing one end of cylinder 20, the plug 52 being sealed with the body 17 by an O-ring 53 and being sealed with the piston rod 24 by seal 54. The piston rod 24 is also reciprocatively mounted in a tubular sleeve 55 that is threadedly attached to body 17 and abuts the plug 52.

The piston head 27 includes a cup-shaped washer attached to the piston rod 24 by a cap screw 56. An expander 57 is provided to engage and hold the washer in its expanded condition so that it effectively engages the peripheral wall of cylinder 20.

The follower 30 is a disc that is attached to and carried by the outer end of piston rod 24. The spring 31 is located about the sleeve 55, one end of spring 31 engaging a collar 60 formed on the sleeve 55 and the other end engaging the follower 30. The spring 31 tends to urge the piston means 23 outwardly toward the one limit so that the follower 30 engages the eccentric 45.

The motor means generally indicated by 61 (FIG. 3) includes an electric motor 62 operatively connected to a speed reducer 63 to the driven shaft 44. Conductors 64 operatively connect the motor 62 in the electrical circuit 16.

The check valve means generally referred to by 65 (FIG. 4) includes a threaded fitting 66 attached to body 17 and located in the chamber 35. One end of valve spring 37 engages the fitting 66 while the other end engages the valve ball 36, the spring 37 tending to urge the ball 36 into sealing relation against the O-ring 67, thereby closing the cylinder outlet 22.

The metering valve means utilized with the embodiment of FIGS. 3 and 4 is of the type illustrated in FIG. 2 and is located adjacent to the rinse line 13 as illustrated in FIG. 1.

It is thought that the operation and functional advantages of this liquid pump have become fully apparent from the foregoing detailed description of parts, but for completeness of disclosure, a cycle of operation will be briefly described. It will be assumed that the liquid pump is not initially primed and that the follower 30 is urged against the eccentric 45 under the action of spring 31.

When it is desired to inject a liquid into a water flow passage, such as injecting a liquid wetting agent into the rinse line during the rinse cycle of a dishwasher, the electrical circuit I6 is energized so as to actuate the solenoid valve 14 to open the rinse line 13 and to actuate the pump motor 61. As the motor 62 is energized, the driven shaft 44 rotates the eccentric 45. Initially, the eccentric 45 urges the piston head inwardly in the first direction. When the pump is filled with air, the needle valve 43 offers little restriction to the air flow from the cylinder outlet 22 and into the rinse line 13, thereby permitting the spring 31 to move the piston rod 24 and piston head 27 through its maximum stroke and in continuous contact with the eccentric 45. After the air is expelled from the pump system and the pump system is primed, the eccentric 45 pushes the piston rod 24 inwardly in the first direction, forcing liquid from the inlet side of the piston head 27 to the outlet side. As the eccentric 45 continues its rotation, the spring 31 moves the piston rod 24 outwardly in a second direction toward the eccentric, but this outward movement is retarded by the discharge flow through the restriction created by the metering valve means 41. As the piston rod 24 and piston head 27 move in the second direction of a delivery stroke, fluid is drawn from the reservoir 32 into the outlet side of head 27.

When the piston rod 24 and piston head 27 are forced in the first direction by the eccentric 45, the pressure is increased slightly on the fluid because there is less displacement on the outlet side of the piston head 27. If the fluid is elastic, as previously described, this positive pressure assures complete filling of the cylinder 20 on the inlet side of piston head 27 The flow rate of the liquid additive 33 into the rinse line 13 is determined by the setting of the needle valve 43 of the metering valve means 41. Because of the restriction to the flow by the metering valve means 41, the piston head 27 will cause only a partial displacement during the delivery stroke in which the head 27 discharges the liquid additive from the outlet side of head 27 through the outlet 22, past the check valve means and into the outlet line. This delivery stroke of the piston means 23 under the action of spring 31 under these operating conditions, will not allow continuous contact with the eccentric 45 during eccentric rotation. When the piston means 23 has been moved outwardly under the action of spring 31 suffciently so that the follower again enters the path of the rotating eccentric, the eccentric 45 will engage the follower 30 and will again push the piston means 23 inwardly in the first direction. This intermittent engagement of the eccentric 45 with the follower 30 and the resultant action of the piston means 23 delivers the liquid additive at a predetermined flow rate.

It will be understood that the piston stroke is not limited by mechanical adjustment for a particular flow rate. The stroke of the piston means 23 is whatever is needed to attain the flow rate determined by the adjustment of the needle valve 43. Adjustment of the delivery rate during the operation is readily accomplished by changing the setting of the needle valve 43. For example, the range of operation in one of the pumps now in operation provide flow rates from 4 cc. per minute to 15 cc. per minute.

If the discharge or outlet line should become blocked, the piston rod 24 will be forced inwardly in the first direction to its extreme limit and will be held in such limit under the pressure of the liquid in the cylinder 20 on the outlet side of piston head 27. In this extreme position, the follower 30 will not contact the eccentric 45 operatively and therefore the motor 62 can idle until normal conditions are restored.

I claim as my invention:

1. In a liquid pump:

a. a body provided with a cylinder having an inlet and an outlet,

b. a piston means including:

1. a piston rod reciprocatively mounted in the body,

2. a piston head carried by the rod and located in the cylinder between the inlet and outlet,

3. means enabling passage of fluid in the cylinder from the inlet side of the head to the outlet side upon head movement in a first direction, and

4. the piston head delivering fluid on the outlet side of the head to the outlet and drawing fluid from the inlet into the inlet side upon head movement in the opposite second direction,

c. resilient means tending to urge the piston means to one limit of its movement in the second direction,

d. motor means engaging the piston means and intermittently urging the piston means away from the said limit and in the first direction, and

e. metering means communicating with the outlet and regulating the liquid flow delivered by the piston means through the outlet to any selected flow rate, the metering means determining whatever stroke length is required during intermittent urging of the piston means to attain the selected flow rate.

2. In a liquid pump:

a. a body provided with a cylinder having an inlet and an outlet,

b. piston means including:

1. a piston rod reciprocatively mounted in the body,

2. a piston head carried by the rod and located in the cylinder between the inlet and outlet,

3. means enabling passage of fluid in the cylinder from the inlet side of the head to the outlet side upon head movement in a first direction, and

4. the piston head delivering fluid on the outlet side of the head to the outlet and drawing fluid from the inlet to the inlet side upon head movement in the opposite second direction, and

5. a follower carried by the piston rod,

c. spring tending to urge the piston means to one limit of its movement in the second direction.

d. a motor means including a rotatable eccentric intermittently engageable with the follower to urge the piston means away fro the said limit and in the first direction,

e. a check valve means communicating with the outlet and enabling fluid flow only in the direction from the cylinder through the outlet, and

f. a metering valve means communicating with the outlet and regulating the liquid flow delivered by the piston means through the outlet to any selected flow rate, the metering means determining whatever stroke length is required during intermittent urging of the piston means to attain the selected flow rate. 

1. In a liquid pump: a. a body provided with a cylinder having an inlet and an outlet, b. a piston means including:
 1. a piston rod reciprocatively mounted in the body,
 2. a piston head carried by the rod and located in the cylinder between the inlet and outlet,
 3. means enabling passage of fluid in the cylinder from the inlet side of the head to the outlet side upon head movement in a first direction, and
 4. the piston head delivering fluid on the outlet side of the head to the outlet and drawing fluid from the inlet into the inlet side upon head movement in the opposite second direction, c. resilient means tending to urge the piston means to one limit of its movement in the second direction, d. motor means engaging the piston means and intermittently urging the piston means away from the said limit and in the first direction, and e. metering means communicating with the outlet and regulating the liquid flow delivered by the piston means through the outlet to any selected flow rate, the metering means determining whatever stroke length is required during intermittent urging of the piston means to attain the selected flow rate.
 2. a piston head carried by the rod and located in the cylinder between the inlet and outlet,
 2. In a liquid pump: a. a body provided with a cylinder having an inlet and an outlet, b. piston means including:
 2. a piston head carried by the rod and located in the cylinder between the inlet and outlet,
 3. means enabling passage of fluid in the cylinder from the inlet side of the head to the outlet side upon head movement in a first direction, and
 3. means enabling passage of fluid in the cylinder from the inlet side of the head to the outlet side upon head movement in a first direction, and
 4. the piston head delivering fluid on the outlet side of the head to the outlet and drawing fluid from the inlet into the inlet side upon head movement in the opposite second direction, c. resilient means tending to urge the piston means to one limit of its movement in the second direction, d. motor means engaging the piston means and intermittently urging the piston means away from the said limit and in the first direction, and e. metering means communicating with the outlet and regulating the liquid flow delivered by the piston means through the outlet to any selected flow rate, the metering means determining whatever stroke length is required during intermittent urging of the piston means to attain the selected flow rate.
 4. the piston head delivering fluid on the outlet side of the head to the outlet and drawing fluid from the inlet to the inlet side upon head movement in the opposite second direction, and
 5. a follower carried by the piston rod, c. spring tending to urge the piston means to one limit of its movement in the second direction. d. a motor means including a rotatable eccentric intermittently engageable with the follower to urge the piston means away fro the said limit and in the first direction, e. a check valve means communicating with the outlet and enabling fluid flow only in the direction from the cylinder through the outlet, and f. a metering valve means communicating with the outlet and regulating the liquid flow delivered by the piston means through the outlet to any selected flow rate, the metering means determining whatever stroke length is required during intermittent urging of the piston means to attain the selected flow rate. 